The present invention is directed to apparatus for forming a receptacle from a precut and prescored flat receptacle blank by the interaction of a mandrel moving in a circular path and a die.
Receptacle forming machines in which a rotating mandrel engages a flat receptacle blank for the purpose of forming a receptacle are old in the art. One of the earliest of such machines is disclosed in U.S. Pat. No. 1,864,632 issued to Bergstein on June 28, 1932. In the Bergstein tray former, a tray blank is positioned on a die by a feeding mechanism. An adhesive is applied to the tray blank and the side walls are folded as the tray blank travels along the feeding mechanism. A rotating mandrel engages the tray blank on the die and passes through both the die and a series of pressure rollers in an arcuate path to form the tray. While the mandrel passes through the pressure rollers, a spring biased plunger for engaging the flaps is actuated by frictional forces between the plunger and the pressure rollers; the plunger engages the flaps of the tray blank and holds the tray. The completed tray is removed from the mandrel by a brush after the plunger disengages the flaps of the tray.
The disadvantages of the Bergstein tray former are typical of the disadvantages of other rotary tray formers in the prior art. In all these tray formers, the mandrel passes through the forming station such as the die and pressure rollers in Bergstein in an arcuate path. As a result, it is very difficult to match the forming operation on the inside radius with the outside radius. For this reason, tray formers such as reciprocating tray formers with a straight line relationship between the mandrel and the forming station are generally preferred. Another disadvantage of prior rotary tray formers concerns the removal of the completed tray from the rotary mandrel without interfering with the path of movement of the mandrel. Prior tray removal techniques often have been cumbersome, unreliable and inefficient. For example, in the Bergstein patent, the tray is removed from the mandrel by rotating brushes which cause the tray to fall through the circular path of the rotating mandrel. Thus, the angular velocity of the mandrel must be limited in order to prevent the mandrel from interfering with the free fall of the tray. Yet another disadvantage of prior rotary tray formers is the limited capability of the mandrel to perform active tray forming functions. Prior art attempts to provide movable elements on a rotating mandrel have been either very limited as in the Bergstein patent or extremely complicated and expensive to manufacture as in the cam operated mandrels described below. Finally, another disadvantage of the prior art rotary tray formers has been the lack of the additional capability of folding and gluing a portion of the tray blank before the rotating mandrel engages the tray blank.
Several recent patents are similar in many respects to the rotary tray former disclosed in the Bergstein patent. For example, U.S. Pat. No. 3,469,508 issued to Klapp on Sept. 30, 1969 shows a rotating mandrel which moves a tray blank through a forming station including a plurality of folding fingers, folding guides and rollers arranged along an arcuate path. A movable cam operated clamp on the mandrel holds the tray blank on the mandrel until the mandrel reaches the discharge station. This clamp is not used for forming any portion of the tray box. Similarly, in U.S. Pat. No. 3,683,755 issued to Lattke on Aug. 15, 1972, the mandrel of a rotary tray former engages a tray blank and passes through an arcuate shaped forming station. The tray is removed from the mandrel by an eject mechanism housed within the mandrel. Thus, these rotary tray formers experience the same disadvantages discussed above.
In several prior art patents, parts of a rotary tray former have been reorientated to overcome some of the disadvantages discussed above. For example, in U.S. Pat. No. 2,821,054 issued to Ritscher on Jan. 28, 1958, a rotating plate adjacent the mandrel for holding the completed package is shown which is partially reoriented for the purpose of removing the package from the rotary tray former. After the mandrel drops the completed package on this separate rotating plate, the rotating plate is briefly reoriented by a cam mechanism to a position parallel to a conveyor belt on which the completed package is placed. However, rather than reorientating the mandrel itself during the formation of the package, the elements which perform the package forming function rotate with the mandrel. In U.S. Pat. No. 2,931,276 issued to Zerlin on Apr. 5, 1960, a rotary tray former is shown in which two or more mandrels are mounted on a support wheel which is pivotally mounted on a rotating lever. As the lever rotates, the support wheel engages a segmented gear mounted on a portion of the circumference of the circular path of the lever. The interaction between the support wheel and the segmented gear pivots the support wheel and the mandrels mounted thereon in order to enable the mandrels to travel different forming paths during successive rotation cycles of the lever. However, since the mandrels in Zerlin are not reoriented while passing through the forming station, the Zerlin tray former does not overcome the disadvantages of an arcuate shaped forming station.
Other prior art attempts to overcome the disadvantages of an arcuate shaped forming station have been directed to enabling the mandrel to provide many of the tray forming functions. For example, a sophisticated mandrel which performs all the tray or package forming functions is shown in the Ritscher patent cited above. The mandrel includes a plurality of forming plates which are movable on the mandrel in response to the movement of a plurality of cams in a stationary cam track. As the mandrel reaches a designated point in the rotation cycle, the cams drive the forming plates which form the package without relying on any fixed forming elements along the arcuate path of the mandrel. Similarly, the Zerlin patent cited above shows a movable pressure lever associated with the mandrel for securing the seam of the container. This pressure lever also is actuated by a rotating cam positioned in a stationary cam track. Although rotary tray formers with cam operated forming elements overcome the disadvantages of an arcuate forming path for the rotating mandrel, these cam mechanisms have several disadvantages. In particular, these cam mechanisms are very difficult and expensive to manufacture. As a result, rotary tray formers with cam operated forming elements attached to the rotating mandrel have not been particularly successful.
It is therefore an object of this invention to provide a rotary receptacle former which overcomes the above disadvantages of the prior art. In particular, it is an object of the present invention to provide a rotary receptacle former in which the mandrel makes a straight line pass through the forming station. In this regard, the orientation of the mandrel of the rotary receptacle former is fixed with respect to the forming station as the mandrel moves in a circular path through the forming station. In addition, it is an object of this invention to provide a movable die at the forming station which tracks the movement of the mandrel by moving radially of the circular path of the mandrel. The object of the combined operation of the mandrel and the movable die is to achieve a straight line pass of the mandrel through the die in order to avoid the prior disadvantages of an arcuate forming path in a rotary receptacle former.
Another object of the present invention is to provide a rotary receptacle former in which the completed receptacle can be quickly and easily removed from the mandrel without interfering with the continuous movement of the mandrel in a circular path. In particular, it is an object of the invention to maintain the mandrel in a fixed orientation with respect to the receptacle removal station as it passes through such station in order to permit a receptacle removal mechanism to remove the completed receptacle from the mandrel without interfering with the continuous movement of the mandrel in the circular path.
An object of the present invention is to provide a mandrel for a rotary receptacle former which has forming elements movable thereon for forming a portion of the receptacle. As a result, the functions of the stationary forming elements in the die can be simplified which results in an increase in the speed of operation of the rotary receptacle former. In particular, it is an object to drive these movable forming elements on the mandrel in response to the reorientation of the mandrel as it moves in a circular path. The disadvantages of cam actuated forming elements on the mandrel are avoided by using a plurality of rotating gears.
A further object of the present invention is to form a portion of the receptacle before the mandrel engages the receptacle blank and the die. In particular, it is an object to form a hem on the receptacle blank before it reaches the die. As a result, completely flat receptacle blanks can be used in the rotary tray former of this invention which results in reduced packing, shipment and storage costs as well as overcoming the aging factor of pre-hemmed receptacle blanks.
Other objects of the present invention include providing a unique and reliable mechanism for forming the corner tabs of the receptacle blank, applying a fast setting adhesive to selected portions of the receptacle blank before it reaches the die to enhance the speed of operation of the rotary receptacle former and providing a fast, efficient mechanism for withdrawing individual receptacle blanks from a stack of receptacle blanks placed on the rotary receptacle former. These and other objects are accomplished by the rotary tray former of the present invention.